The overall aim of these studies is to identify the causative agent of Acquired Immune Deficiency Syndrome (AIDS). The main organism under study will be human cytomegalovirus, but the experiments are designed to enable detection of other known viruses e.g. Epstein-Barr virus (EBV), Herpes Simplex virus (HVS) and human papilloma virus (HPV) and novel agents, so far undetected. The persistence of viral nucleic acids and viral-specific proteins will be examined by Southern blotting, dot blotting, in situ hybridization, immunoprecipitation and immunofluorescence. The recently developed procedures utilizing biotin-avidin labelling will be employed in the examination of tissues obtained for pathologic diagnosis. The hybridization probes will be cloned sub-genomic fragments of viral DNA, selected to avoid non-specific results consequent upon known homologies with human DNA. AIDS and Kaposi's Sarcoma tissues will be examined in the electron microscope for viral and unusual cellular structures, e.g. vesicular rosettes and tubulo-reticular structures, and EM preparations will be hybridized with viral probes in attempts to identify viral components in these structures.